What are the benefits and risks of taking quercetin as a dietary supplement for inflammation and heart health?

Quercetin Supplementation: Benefits and Risks for Inflammation and Heart Health

Current evidence does not support the routine use of quercetin supplementation for cardiovascular disease prevention or inflammation reduction, as high-quality guidelines explicitly state that dietary supplements including quercetin are not beneficial for reducing acute cardiovascular events. 1

Guideline-Based Recommendations

Cardiovascular Disease Prevention

• The 2023 AHA/ACC/ACCP/ASPC/NLA/PCNA guidelines for chronic coronary disease explicitly state that nonprescription dietary supplements are not beneficial to reduce the risk of acute cardiovascular events. 1
• This recommendation applies to quercetin along with omega-3 fatty acids, vitamins C, D, E, beta-carotene, and calcium. 1
• The evidence emphasizes obtaining nutrients from whole foods rather than isolated supplements—a diet emphasizing vegetables, fruits, legumes, nuts, whole grains, and lean protein is recommended instead. 1

Perioperative Considerations

• Quercetin should be held 2 weeks before surgery according to the Society for Perioperative Assessment and Quality Improvement (SPAQI) consensus statement. 1
• The rationale includes anti-inflammatory effects demonstrated in animal models and potential interactions with medications such as cyclosporine, pravastatin, and fexofenadine. 1
• Patients with estrogen-dependent cancers or kidney dysfunction should avoid quercetin supplementation. 1

Dietary Sources vs. Supplementation

Food-Based Polyphenols

• Quercetin is a dietary polyphenol naturally found in fruits, vegetables, and whole grains, with typical adult consumption reaching up to 1 gram of total polyphenols daily from food sources. 1
• Dietary polyphenols from whole foods demonstrate anti-inflammatory and antioxidant properties, encourage growth of beneficial gut bacteria (Lactobacillus and Bifidobacterium), and may lower the Firmicutes-to-Bacteroides ratio associated with obesity. 1
• The gut microbiota processes polyphenols into bioactive, low-molecular-weight compounds that enhance host health—this transformation is essential for their beneficial effects. 1

Supplement Limitations

• Most dietary supplements lack convincing evidence for health benefits, and certain supplements have been shown to be harmful. 1
• The current evidence does not support using dietary supplements to duplicate the cardioprotective benefits of consuming healthful foods. 1

Research Evidence on Quercetin Supplementation

Clinical Trial Findings

• A 2021 randomized controlled trial in 88 post-myocardial infarction patients found that 500 mg/day quercetin for 8 weeks significantly increased total antioxidant capacity and improved the insecurity dimension of quality of life, but failed to show significant effects on inflammatory markers (IL-6, hs-CRP), blood pressure, or other quality of life dimensions. 2
• TNF-α levels decreased within the quercetin group but this was not significant compared to placebo. 2

Mechanistic Properties

• Quercetin exhibits antioxidant, anti-inflammatory, and potential cardiovascular benefits through multiple mechanisms including free radical scavenging, inhibition of inflammatory cytokines, and effects on the NLRP3 inflammasome. 3, 4, 5
• Laboratory and animal studies suggest benefits for mitochondrial biogenesis, oxidative stress reduction, and cellular protection. 6, 5

Clinical Bottom Line

For inflammation and heart health, prioritize a whole-food dietary approach rich in quercetin-containing foods (fruits, vegetables, whole grains) rather than isolated quercetin supplements. 1

Practical Approach:

• Emphasize dietary sources: Consume vegetables, fruits, legumes, nuts, and whole grains that naturally contain quercetin and other beneficial polyphenols. 1
• Reduce saturated fat to <6% of total calories and minimize sodium to <2,300 mg/day (optimally 1,500 mg/day). 1
• Avoid trans fats completely as they are associated with increased morbidity and mortality. 1
• Limit refined carbohydrates and sugar-sweetened beverages to reduce cardiovascular risk. 1

Important Caveats:

• If considering quercetin supplementation despite lack of guideline support, discontinue 2 weeks before any surgical procedure. 1
• Avoid in patients with estrogen-dependent cancers, kidney dysfunction, or those taking cyclosporine, pravastatin, or fexofenadine. 1
• Most information on quercetin benefits derives from in vitro and animal studies rather than robust human clinical trials. 6
• The single positive human trial showed modest benefits limited to antioxidant capacity without meaningful improvements in inflammation or cardiovascular parameters. 2